The wi-fi offering, provided by T-Mobile, lets passengers access the internet at speeds of up to 2Mbps en route to the world's busiest international airport. The trains connect back to the T-Mobile network using a 3.5G HSDPA cellular connection, or WiMax when in a tunnel.

To access the service, customers need to purchase a T-Mobile HotSpot card with prices starting from 75p for 10 minutes to £40 for 30 days of wi-fi access.

Customers can then use the wi-fi network for the train journey from Paddington to Heathrow, as well as at hotspot zones in the airport, the train stations and elsewhere in London.

Photo credit: Gemma Simpson

Published: April 24, 2007 -- 15:42 GMT (08:42 PDT)

Caption by: Gemma Simpson

The wi-fi service is aimed at business travellers, to give them the ability to access emails and the internet during the short time they have travelling to and from Heathrow airport.

Brian Raven, managing director at Heathrow Express, said people may ask why it is necessary to have wi-fi connectivity on a 15 minute train journey but people use the Heathrow Express service because they are trying to save time.

Raven added: "Minutes of not working are lost minutes for the bankers, traders and other business professionals using this train service."

Photo credit: Heathrow Express

Published: April 24, 2007 -- 15:42 GMT (08:42 PDT)

Caption by: Gemma Simpson

The wi-fi service provides connectivity for the entire journey, including a stint through a 6km tunnel. The network was designed and installed by mobile network provider Nomad Digital.

Nigel Wallbridge, founder and chairman of Nomad Digital, said this is the first time WiMax has been used to provide a wi-fi network to a train within a tunnel and this opens up the possibility of using this technology on underground trains in London and worldwide.

Wallbridge told silicon.com there are many other applications for wi-fi enabled trains including using live CCTV to warn the driver of any problems within the train's carriages and providing up-to-date travel information to passengers via television screens in the train carriages.

He predicted every train operator around the world will be offering a wi-fi network in five years' time.

More than 15,000 passengers use the Heathrow Express service each day and more than 40 million people have travelled on it since the service launched in June 1998.

The wi-fi offering, provided by T-Mobile, lets passengers access the internet at speeds of up to 2Mbps en route to the world's busiest international airport. The trains connect back to the T-Mobile network using a 3.5G HSDPA cellular connection, or WiMax when in a tunnel.

To access the service, customers need to purchase a T-Mobile HotSpot card with prices starting from 75p for 10 minutes to £40 for 30 days of wi-fi access.

Customers can then use the wi-fi network for the train journey from Paddington to Heathrow, as well as at hotspot zones in the airport, the train stations and elsewhere in London.